#ASKDRTAN: Psychology Professor Answers Your Questions Via Social Media

Siu-Lan Tan, Ph.D., first author of leading text Psychology of Music: From Sound to Significance, answers your questions.

You might recall  this video  of a baby moved to tears by her mother’s singing popping up on your newsfeeds earlier this year. Dr. Siu-Lan Tan’s analysis of that video from the perspective of a child psychologist and psychology of music professor was a must-read on two popular blogs in 2013. Now we’re inviting you to watch another video that’s been popular recently, ask Dr. Tan your questions about it and qualify to win a prize!

Watch these twin babies dancing to their father’s guitar:

Twin girls were filmed every August for 3 years as they responded to their father playing his guitar. The videos went viral with over 22.6 million views, and 1+ million views; and the third video was posted just 2 months ago.

Take a look at the twins at (almost) 1 year, 2 years and 3 years old. What questions come to mind about their behavior and about early responses to music? See below for details on how to send questions and qualify to win a prize!.

Send us your questions via Twitter using the official hashtag #ASKDRTAN before or after your question. Dr Tan will receive all questions* placed before October 29 via Psychology Press’ Twitter and Facebook accounts. If your question is selected as one of Dr Tan’s top picks, you will receive a free copy of her book, Psychology of Music: From Sound to Significance, and your questions will also be fully developed as part of an article to be published on our website and on her Psychology Today blog, What Shapes Film?

#ASKDRTAN Question Example:


Dr. Siu-Lan Tan is first author of a leading text entitled Psychology of Music: From Sound to Significance.

Born in Indonesia and raised in Hong Kong, she earned degrees in piano and music before attending Purdue University, Oxford University, and Georgetown University to complete an MA and PhD in psychology. She is now a senior Professor of Psychology at Kalamazoo College, where she teaches courses on creativity, psychology of music, and developmental psychology.

Her work has been published in Music Perception, Psychology of Music, Psychomusicology: Music, Mind, and Brain, Empirical Musicology Review, International Journal of Gaming and Computer-Mediated Simulations, and Journal of Applied Developmental Psychology, among other journals.

*Dr Tan can only answer a portion of questions during the week, but will try to cover the most popular and central questions in her full commentary.

Hey, We’re in Sync!

Great questions via Twitter and Facebook! They made me think more deeply about these videos. If your questions weren’t chosen for today’s response, it doesn’t mean they weren’t valuable. And they’re still in the running for a prize at the end of the week!

On the first day of #ASKDRTAN week, many focused on the look the twins exchanged as soon as the music started, and their seemingly matching (synchronous) movements.

@zooeats and @teobesta were struck by how the infants look at each other as soon as the music begins in the first and third videos. @Allison_M_Bloom asked whether the twins are mimicking each other, and @savannahhhas was puzzled by how they might be forecasting what the other was about to do “even before it happens”, leading @kelseydonk and her friend Olivia to view their movements as having a “choreographed quality”.

These observations are all related! What you are witnessing is what sibling researcher and psychologist Dr. Judy Dunn calls “coaction”. Dunn observed that siblings often engage in episodes in which they seem to be “doing things together at the same time” – in other words, matching each others’ actions simultaneously. For instance, two siblings may be sitting in high chairs, and one begins to bang on the tray table – and quickly the other begins to hit their table too – and swiftly they match each others’ rhythms – and begin to giggle. This is “coaction”. Looking and glancing at each other frequently is an important part of this social coordination, which is actually one of the earliest forms of play with a partner.

You can observe “coaction” especially clearly in the third video (35 months):

0:11: Looking at each other
0:16: Right twin clasps hands; 0:18 Left twin clasps hands
0:20: Left twin copies swishing motions with hands, then clapping
After “go” at 0:25, movements become more individualized (with some imitation at 0:40 of pointing).

Before each of these, the girls look at each other (except for at 0:40 when gaze is not met, and nor is coaction fully activated)

So yes, Alison is right that they are imitating each other. And yes, Savannah, at times they may even be “forecasting” movements – by reading each other for short spurts as they’re familiar with this piece of music and have likely responded with similar actions before. This “choreographed quality” that Kelsey and Olivia observed may come partly from their responses to the way the music choreographs their actions (a subject of an upcoming post…!). But the other aspect is a sort of “social choreography” that is patterned by the two of them, matching actions to each other. While Dunn’s research focused mainly on siblings, one can imagine that coaction might be even stronger in twins.

One characteristic feature observed by Dunn is that “coaction” seems to trigger great glee! She describes “the special pleasure and excitement expressed by siblings when they engage in ‘coaction sequences’ together” (Dunn, 1983, p. 792). This utter glee and delight during coaction is clearly shown in our “dancing twins.”

More about the role of the music, twin behavior - and many more connections to the videos - coming in the full commentary to be posted soon after #ASKDRTAN week ends. In the meantime, please keep your questions coming!

– Dr Siu-Lan Tan


Dunn, J. (1983). Sibling relationships in early childhood. Child Development, 54, 787-811

© 2014 Siu-Lan Tan

Moved by Music

Day Two of #ASKDRTAN week brought a treasure trove of intriguing questions! Yesterday, I addressed questions about the surprising synchronicity of the twins’ movements – by discussing “coaction”. 

A new theme emerging from your questions focuses on the early beginnings of engagement with music (@drewtetz) and the increasing variety of expressive movements you observe in the twins at almost age 1 year, 2 years, and 3 years.

Michael on Facebook said: “I'm fascinated by how the twins seem to be building a "repertoire" of dance expressions as they grow.”

And Barbara on Facebook pinpointed a dramatic change between the twins at 11 and 23 months: “What are the key developmental changes occurring between time one and time two that explain the way they use their whole body in responding to the music?”

Part of the answer may be found in @KingMedian’s conjecture on Twitter: “Does gross motor development aid in infants' understanding of keeping tempo?"

“Gross motor development” refers to attainments in our ability to perform actions that engage most or all of the body – such as sitting, standing, walking, running. And indeed, as each of these budding abilities blossom, they open up new possibilities in the “repertoire of dance expressions”.

For instance: By around 6-7 months, when most infants start to sit up, they begin to respond to rhythmic music – by nodding or shaking their heads, and moving their torsos (pulsing, bouncing, or swaying like the twins). Here’s a great example of 10 month-old Diogo responding to a rhythmic Beatles song. (Though he receives encouragement from his dad to sustain his bouncing, the impetus seems to be spontaneous).

Next: As infants begin to stand up and then walk (10-12 months), they often begin to bend the knees to rhythmic music or make stepping motions with alternating feet. And as they approach 2 years, their refined sense of balance and mobility frees them to tiptoe, run, twist, and spin to spirited music. This is charmingly illustrated by the girls (the same “dancing twins” as in our trio of videos) seen here at 19 months:

The “dancing twins” respond to the same guitar song as in their 11 month-old video – but at 19 months, they are old enough to move about freely. The repetitive swaying has progressed to a variety of twirling, twisting, and a range of arm movements, inspired by the music. Each new gross motor skill “unlocks” new potentialities in expressive movement. In turn, @RachelMariiie ’s intuitions that the twins’ motor (muscle, movement) development may be enhanced by their exposure to music, seems right on target.

However, to address @kajopee’s question about whether musical rhythms shape the infants’ movements, and especially @shananigans010’s question “is rhythm a skill we are born with?”: Notice that the movements are not yet synchronized to the beat of the music. Although a recent 2014 study by Fujii et al. showed that a portion of 3- and 4- month old infants demonstrate “sporadic synchronization” (brief moments of limb movements matching the beat) – truly moving in synchrony to music is rarely seen before age 4 years. It is really the spirit of the music that our dancing twins so joyfully embody in the videos that have captivated more than 20 million people.

Please keep sending your inspiring questions!

– Dr Siu-Lan Tan


Fujii, S., Watanabe, H., Oohashi, H., Hirashima, M., Nozaki, D., & Taga, G. (2014). Precursors of dancing and singing to music in three- to four-month-old infants. PLoS ONE 9(5): e97680. doi:10.1371/journal.pone.0097680

Chapter 9, Psychology of Music: From Sound to Significance

© 2014 Siu-Lan Tan

An Affinity for Music

My third installment follows after a few days’ of great questions – including our first submission by a child, 9-year-old Max!

Part 3 is inspired by Daniela’s question via Facebook and @madasilva on Twitter: Is it a normal reaction or could we start to think that [the twins] are prodigious for the music?

While my last two posts explored common social behaviors (imitation and “coaction”, in Part 1) and natural milestones in infants’ movements to music (Part 2), we now turn to some surprising elements of the videos. To what extent might the twins’ expressive movements reflect their musical sensitivity?

(1) Sensitivity to beat

In my previous post (Part 2), I mentioned that many researchers have found that it is not until 4 years or older that most children begin to synchronize movements to music. Of course there are exceptions, but they are rare.

However, infants can match the beat for short spurts (i.e., “sporadic synchronization”) – especially if the music is strongly rhythmic and fits the fast tempo (pace) of their natural movements. We can observe this in the video at 23 months, when the twins are bouncing in perfect time with the opening section of the music.

Personally, I was quite surprised by the twins’ ability to bounce exactly in time with the music and each other (as well as some wriggles and hand movements that reflect the beat). But it’s possible that the music happened to be close to the twins’ natural bouncing rate. Being seated in chairs also limits movement possibilities, which can increase matches with music. (This is why we may see more synchronicity to music than in the video of the twins dancing in a standing position at 19 months [see video in Part 2]).

Also, an important element in all three videos is that they’re responding to live performances by their Dad. As many researchers (such as Jane Davidson) have shown, performers naturally convey something about musical structure through their movements – in obvious or subtle ways – which could have been picked up by the girls. This possibility was also raised by @drchromo via Twitter. Still, the twins show a very good sense of beat as children cannot always copy the beat/pulse of adults even when there is a live model.

Taking the discussion to a more fundamental level: @jantonishen, @DrSallyKazoo, @PlanetZooFilms and @steph_finnern on Twitter and Logan Horejsi on Facebook all asked whether a sense of musical structure, a feeling of beat, or the body’s ‘dance’ response to music may be innate – i.e., not requiring learning, and even perhaps hard-wired into the species. If so, is dancing and synchronizing to a beat a purely human ability?

A few years ago, some researchers were captivated by this YouTube video of a cockatoo named Snowball, dancing to “Everybody” by the Backstreet Boys:

Some time after this video was posted, neuroscientist Aniruddh Patel and colleagues (2009) began to study Snowball’s ability to synchronize to the beat of music. They were careful to use a recording of the music (eliminating live performers’ cues). Also, they created 12 versions, each at a different tempo (speed or pace). By changing the tempo of the music, they could see whether Snowball could adjust his rhythmic movements to match the changing speed of the music (and yes, he could!). In a painstaking analysis, every head bob was analyzed in relation to the music. The researchers even went through an extra step to make sure synchronicity did not happen by chance, by analyzing the head-bobbing against other versions to which Snowball was not dancing. So no, it seems “synchronization to a musical beat is not uniquely human” (p. 827).

(2) Sensitivity to general musical structure

Back to our twins: Our youngest submitter so far, 9-year old Max (via Twitter), observed: As the music changed, the twins danced differently. How much of that was just the music or was it something else?

Indeed, another thing I found to be noteworthy about the girls at every age was their ability to capture the spirit of the music. The broad features of each song are reflected in their movements, especially changes at new sections. For instance in the video of the twins at 23 months (shown above), they immediately respond with large body movements (forceful bouncing, swaying) to the rhythmic section of “their new favorite song”. But at 0:32 - when the music becomes lighter and more melodic - the large body movements cease and give way to smaller arm movements, and more delicate wriggles of the body. By 0:42, when a cadenza begins without a well-defined pulse, their movements become less patterned and attention wanes.

Again, as they are watching a live performer, their Dad’s natural facial expressions and body movements could have telegraphed changes in the music. But it still takes musically sensitive children to match those cues to the music and to their body movements. Further, the twins also influence each other through imitation and coaction (discussed in Part 1).

So as Kaeli on Facebook, @steph_finnern via Twitter, and Max conjecture, there may be other (especially social) influences that are shaping the girls’ responses to music – though these are likely complementing the twins’ own musicality and enjoyment of music. One must also remember that the social cues are, in fact, an inherent part of learning to understand and appreciate music.

Back to Daniela’s opening question: I don't use "exceptional" or “prodigious” easily – as I find all children exceptional and prodigious in some way. But I will say that I found many elements of the girls’ responses to music to be remarkable and surprising, and I hope that their parents will continue to nurture the twins’ great love and enjoyment of music that have inspired us all.

Please keep your questions coming! We are accepting them till Wednesday Oct. 29!

– Dr Siu-Lan Tan


Patel, A. D., Iverson, J. R., Bregman, M. R., & Schultz, I. (2009)*. Experimental evidence for synchronization to a musical beat in a nonhuman animal. Current Biology, 19, 1-4

*Includes supplemental film showing Snowball synchronizing to three tempi

Snowball™ Irena Schulz of Bird Lovers Only, Inc.

Chapter 8, 9, Psychology of Music: From Sound to Significance

© 2014 Siu-Lan Tan

Duple Time

During our #ASKDRTAN week, I have fielded questions from students, a 9 year-old child, and professionals in many parts of the world – including twin researchers and musicologists. This spectrum of questions inspired new insights on our dancing twins that I would not have thought of alone. For Part 4, we turn to these two questions:

@DrChromo (an epigenetics researcher) inquired: Has anyone studied v young DZ and MZ twins' response to music?

@Jhang_12 (a student in introductory psychology) asked: What role does “the environment raised within” play in the reaction of the twins to the music?

There are few published twin studies focusing on musicality. Aside from the rarity of twins in the population, there is the difficulty of defining and ‘measuring’ musicality – in any of its forms - including potential, or ability, or accomplishment. Plagued with the same, if not greater, complexities as defining ‘intelligence’ or ‘creativity’, there does not seem to be an easy way to determine one’s level of musicality.

Although we often refer to it in a singular fashion (“she has great musical ability”), musicality really seems to be not one, but a whole set or constellation of abilities. Is it an accurate ear for pitch and melody? Is it a good sense of rhythm? Is it dexterity, refined motor skills? A knack for expressive and sensitive interpretation? A deep capacity for responsiveness and enjoyment of music? Probably all of these and more.

Of the few existing twin studies, some have focused on a specific skill – especially pitch perception. For instance, Dennis Drayna and colleagues asked 136 pairs of identical twins and 148 fraternal twins (between 18 and 74 years old) to listen to 26 popular melodies and detect whether each contained an incorrect pitch or not. (This is known as the Distorted Tunes Test or DTT, a version of which can be found at this NIH site). The correlation of DTT scores for the identical (monozygotic) twins was higher than for the fraternal (dizygotic) twins. Heritability was 71% to 80%, depending on which technique was used for genetic model-fitting.

Similarly, in examinations of rare musical abilities such as absolute pitch or perfect pitch (the ability to identify musical tones – “that’s an F#!” - without being given a reference pitch), studies often reveal higher concordance rates for incidence in monozygotic than dizygotic twins (e.g., Theusch & Gitschier, 2011). There are also earlier studies examining similarities in twins such as musical interest, performance in and out of school, and musical achievement (such as Coon and Carey in the 1980s, which emphasized the contribution of shared family environment over shared genes). And no, @drchromo, we don’t have a body of published studies yet focusing on musical development in very young twins.

[Maybe these other twins are conducting research on the dancing twins?]

But if heritability seems so important, does practice and training count for much?

A couple decades ago, academics tended to swing toward the “talent” assumption (i.e., one’s level of achievement is primarily determined by genetic endowment) or views that challenged it. For instance, K. Anders Ericsson and colleagues did not deny that genetics or inborn ability played a role, but argued that the role of innate capacities in achieving superior performance had been grossly overemphasized. In a 1993 paper, Ericsson et al. showed that violin students at a prestigious West Berlin conservatory who reached the ‘best’ level of achievement had spent more time on deliberate practice than those in the ‘good’ or lowest-achieving group (7,400 versus 5,300 and 3,400 hours). This was not just time logged on the violin engaged thoughtlessly in mere repetition - but concentrated “deliberate practice”, which is highly-structured practice, with clear goals and strategies to address weaknesses and improve performance.

However, the separation between “genetics” versus “practice” has recently come into question. Could the propensity for long hours of effortful practice also have a genetic basis? Could genes influence what results we glean from an hour of practice, therefore motivating us to practice more – or less? In a recent brief report examining over 800 sets of same-sex twins, Hambrick and Tucker-Drobo (2014) reported a genetic effect on music practice: “It is likely that genetically influenced penchants and/or aptitudes for music could lead children to dedicate themselves to music practice” (p. 4, italics added).

In a surprising 2014 study, Miriam Mosing and colleagues studied 10,500 (monozygotic and dizygotic) twins aged late-20s to mid-50s – focusing on the relationship between music practice and musical ability. They found “no difference in ability within monozygotic twin pairs differing in their amount of practice, so that when genetic predisposition was controlled for, more practice was no longer associated with better music skills” (p. 1795). In other words, even when one identical (monozygotic) twin had accumulated thousands more hours of practice over their lifetime than the other, both twins tended to score similarly on tests of musical ability – namely: a pitch discrimination test, a melody test (detecting one note difference in short melodies), and a rhythm test.

I am a strong believer in effort and do not wish to be misconstrued to have said that practice does not count! Note that the Mosing study did not focus on music achievement or accomplishment as their measure. This study showed that scores on basic tests of musical sensitivity did not differ with practice. However, certainly an identical twin who has only tinkered on the piano for a year, and one who has trained for several years, would reach different levels of achievement on their musical instrument.

Twin researcher Dr Nancy Segal asked on Facebook: Twin studies reveal genetic effects on virtually all measured traits. Do you think the twins would respond do similarly if they heard the music alone, away from their twin?

Would the “dancing twins” (who, by their parents’ report, are identical) move the same way to the music in the absence of the other? It is difficult to say. In these videos I see at least two forms of choreography - one matching to the music (which I discussed in Part 3) and the other a sort of “social choreography” (matching to each other) – which I addressed in Part 1. Karyn Boatwright on Facebook and @qoekfquf1212: There is more than imitation and turn-taking; we can observe “co-action” (see Part 1 for “co-action”). All thinking alike, @Brummiel, @kyra_blum, @jantonishen, and @Allison_M_Bloom pondered whether non-twins could also show matching dance movements. Actually, “co-action” was first identified by a sibling (not twin) researcher, and is common also in peers. The mutual look and constant sideway glances play an important role in “coaction” (as noticed by @lisalombardphd , @TGL_BoF, and Kyle Hahn on Facebook).

I would expect more similarities in movement responses would be seen early in infancy (for instance, nodding and movements of the torso) but as new fine and gross motor skills are increasingly achieved (as covered in Part 2), we may expect to see greater individuality. On the level of detail (the particular movements) I may expect variation, but on basic structural elements (outlined in Part 3- feeling of beat, tempo, character and mood of the music, changes at the beginning of a new section), I would expect some similarity in the absence of the twin. But this is conjecture.

In the end, as we reflect on our delightful “dancing twins”, we are far from understanding the complexities of the nature-nurture question in musical ability or achievement. Clearly, much more research is needed to understand the role of genes and environment, and how they are enmeshed in this complex and multifaceted thing we call musical ability. We look hopefully to twin researchers to pursue this exciting avenue for future research.

Thank you for all your inspiring questions! Today is our LAST day for questions for #ASKDRTAN, ending at midnight (in your time zone) on October 29, 2014. Questions received today may still be answered in my final post, next week – along with announcement of prizes for top questions!

– Dr Siu-Lan Tan


Drayna, D., Manichaikul, A., de Lange, M., Snieder, H., & Spector, T. (2001). Genetic correlates of musical pitch recognition in humans. Science, 291, 1969-1972.

Ericsson, K. A., Krampe, R. Th., & Tesch-Römer, C. (1993). The role of deliberate practice in the acquisition of expert performance. Psychological Review, 100, 363-406

Hambrick, D. Z., & Tucker-Drob, E. M. (2014). The genetics of music accomplishment: Evidence for gene-environment correlation and interaction. Psychonomic Bulletin & Review. (Online brief report June 24, 2014)

Mosing, M. A., Madison, G., Pedersen, N. L., Kuja-Halkola, R., Ullén, F. (2014). Practice does not make perfect: No causal effect of music practice on music ability. Psychological Science, 25, 1795-1803

Theusch, E., & Gitschier, J. (2011). Absolute pitch twin study and segregation analysis. Twin Research and Human Genetics, 14, 2, 173–178

Distorted Tunes Test on National Institutes of Health site: http://www.nidcd.nih.gov/tunetest/Pages/Default.aspx

Ch 10, Psychology of Music: From Sound to Significance

© 2014 Siu-Lan Tan

Follow My Lead?

During #ASKDRTAN week, we shared some captivating videos with you and invited you to submit questions about them.

This “trio” of viral videos fascinated me, given my background in child development and psychology of music – and I was eager to share them with you! Two twin girls were filmed every August for 3 years, as they responded to their father playing his guitar – in a set of videos that have been viewed over 24 million times.

I used your questions to shape four Q & A posts about these videos, but saved the most frequently-asked one for my final post.

What was the most popular question?

We received questions via Psychology Press Twitter and Facebook from students, professors, and renowned researchers in several countries, and even a 9 year-old called Max.

So, what was the most popular question emerging from #ASKDRTAN week?

There seems to be a dominant child in the videos. The twin on the left seemed to be glancing over at the twin on the right for guidance. Does the dominant child dictate how both of them dance or do they react independently to their dad playing the guitar? – Alexis F (via Facebook)
It seems to me that the twin on the left follows the one on the right. Is there such a thing as a dominant twin? – @PlanetZooFilms (via Twitter)

[Similar questions were submitted by many others, including by Lia W and Logan H and Kyle H and Karyn B on Facebook and @Ben_Forhan and @amanlyant and @Kat_Russell321 via Twitter]

Is there a dominant twin? Is one “dancing twin” copying the other?

The question about whether there may be a “dominant twin” seems to fascinate the public more than twin researchers. It is not a strong focus of current research and most studies on this topic were published in the 1950s or 1960s. Still, it is an intriguing question as it relates to our “dancing twins”!

First, there is the question of what is meant by “dominant” – Is it the firstborn twin, the twin that is larger in stature, the one who is first to cut a tooth or sit or walk independently?

For instance, when it comes to stature, the interaction between “nature and nurture” begins long before birth. Even identical twins are not strictly genetically identical at birth, due to copy number variation, or to conditions in the womb. One twin may be more favorably positioned in the womb to receive oxygen and nutrients from the placenta than the other, or to move around more freely. Some twins share the same amniotic sac; others may each be “housed” in separate amniotic sacs; some twins share the same placenta and some receive sustenance from different placentas. So even identical twins may differ in size and physical development at birth – as the interaction of genes and environmental influences (“nature and nurture”) are already at play in the womb.

Or – by “dominant twin” do we mean the one who is more socially dominant? In the case of our “dancing twins,” many asked whether one twin primarily initiates the movements while the other tends to copy her?

Piontelli and colleagues found that among both identical and fraternal pairs of twins, one twin is often more active than the other – even before birth. They found that by 10 weeks old, one fetus was significantly more active than the other in 29 out of 30 pairs of twins they monitored by ultrasound scans. The active twin was also less reactive to the other twin’s movements (perhaps because the other moved less) – and this was already apparent about 7 months before birth.

However, does the active twin initiate corresponding movements in the other twin? In another prenatal study, Sherer and colleagues monitored 30 twins and “failed to reveal evidence of a dominant twin in utero” (p. 460). The incidence of one twin “initiating the majority of coinciding fetal movements with statistical significance” was found for only 3 out of the 30 pairs of (identical and fraternal) twins.

But what about expressions of ‘dominance’ in more complex behaviors after birth? As I mentioned before, there are not many recent studies on this topic. One study reported in 2003 by Ebeling and colleagues, employed questionnaires completed by 22-30 year-old twins in a longitudinal study in Finland. Ebeling et al. examined different kinds of dominance – physical, psychological, and verbal – and their longterm implications.

They found that during adolescence, male twins reported dominance in the physical domain whereas female twins reported more psychological dominance (e.g., who decides on shared opinions, or serves as the “spokesperson”). With increasing age, however, they found that “dominant and submissive features are more likely to level off, and twins become more and more equal in their actions and behaviors” (p. 341). So even if there is such a thing as a more dominant twin, the differences seem to diminish over time.

Complementary roles

The notion of a "dominant twin" seems to be an oversimplification of the complex interactions of twins. As Ronald Wilson – author of another longitudinal study (Louisville Twin study) has explained, each twin probably "rules" over different domains (e.g., one may be more verbally dominant, while another may be more physically dominant, or a twin may be more dominant in decision-making in one area but not another). Rather than dominance, there may be complementarity.

For instance: As we watch the same “dancing twins” at play here at 9 months, the twin on the left may seem to be the initiator at first glance, as she plays the role of the lure in their game of ‘you can have it; no you can’t’. However, the other twin is just as active and shows just as much initiative in her attempts to ‘steal’ the rattle. Nor can we assess relative physical strength as the green handle is perfectly shaped for a baby’s ulnar (whole hand) grasp; the other twin’s strong hold on the odd-shaped knob is equally impressive. As I see it – just as in a dance – this interchange is marked by a complementarity of roles and equally active engagement. (I should also point out that – as if to foreshadow their viral videos – the rattle they are playing with is a guitar!)

Follow the music

When it comes to the trio of videos for the “dancing twins,” there is also the role of the music in coordinating their movements. Sandra Trehub (1993) found that faster, rhythmic, rousing music (such as marching band-type music) elicited more spontaneous bouncing movements in infants of about 1 year old than slow, flowing, gentle music. So the rhythmic guitar music being played to the “dancing twins” is quite optimal for eliciting motor responses in the girls, and provides a structure for them to coordinate and match their movements together. (See also Tan, Pfordresher, and Harré, 2010, chapter 9) [This answers questions on tempo by @mattbezdek, @KZooAndrew, and @siaaaLaterrr, and style by Gunyeop L on Facebook]

In the last video, the girls are almost 3 years old and most of their movements reflect the tempo/pace of the music (as discussed in Part 2 and Part 3). As they grow, we can expect their movements to express more parameters of music, as Kohn and Eitan (2009) showed that 5- to 8-year old children increasingly reflect features of music in their body movements. In particular, increase in loudness (and to a lesser extent, rising pitch) is typically depicted by increasing speed of movement, energy, and rising and forward movements. [This answers a question for @Sean_Peterkin ]

So is it possible that one of our “dancing twins” may reference the other more during "co-action episodes" [see Part 1]? Or show more initiative in how the body moves to express parameters of music [see Part 2], or in the sensitive interpretation of features of the music [see Part 3]? Yes, it is possible. But can we draw any conclusions about their general level of so-called 'dominance' or ‘leadership’ within the pair - or each twin's relative musical aptitude [see Part 4]? Most likely not.

It is a delight to watch these twin girls develop and to appreciate them as individuals, each with their own strengths – musical and other. The videos of the twins dancing to their dad’s guitar at (almost) 1 year, 2 years, and 3 years, are gems: A celebration of the pure joy of music and a marvelous record of early development. And we can only hope for another window into their lives in August 2015!

Congratulations to our winners

Thanks to all who participated in #ASKDRTAN! In all, I responded to about 50% of your questions within themes that shaped my Q&A posts. It was not easy to select the winners for our best question awards as all your questions were intriguing.

Here are the winners for #ASKDRTAN - who will each receive a copy of my book Psychology of Music: From Sound to Significance:

  • @Brummiel – fundamental question separating twin and general musical responses
  • @communikatt – insightful connections between musical and social behavior
  • @jantonishen – two most resonant questions, central to psychology
  • Lia W on Facebook – many extremely keen observations
  • @Sean_Peterkin – four great questions about early musical abilities
  • @teobesta – I would like to give you the spirit award for your enthusiasm, support, personality

My thanks again to all who participated, and to Trish Pomar at Psychology Press.

– Dr Siu-Lan Tan


Ebeling, H., Porkka, T., Penninkilampi-Kerola, V., Berg, E., Järvi, S. & Moilanen, I. (2003). Intertwin relationships and mental health. Twin Research, 6, 334-343

Kohn, D., & Eitan, Z. (2009). Musical parameters and children’s movement responses. In J. Louhivuori, T. Eerola, S. Saarikallio, T. Himberg, & P. S. Eerola (Eds.), Proceedings of the 7th Triennial Conference of European Society for the Cognitive Sciences of Music, (pp. 233–241). Jyväskylä, Finland: ESCOM

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Sherer, D. M., Nawrocki, M. N., Abramowicz, J. S., Peco, N. E., Metlay, L. A., Woods, J. R. (1992). Is there a “dominant twin” in utero? American Journal of Perinatology, 9, 460-463

Tan, S.-L., Pfordresher, P., Harré, R. (2010, 2013). Psychology of Music: From Sound to Significance. Hove/New York: Psychology Press

Trehub, S.E. (1993). Temporal auditory processing in infancy. Annals of the New York Academy of Sciences, 682, 137-149

© 2014 Siu-Lan Tan

About Dr Tan

Dr. Siu-Lan Tan is first author of a leading text entitled Psychology of Music: From Sound to Significance, and has published research in numerous journals. She is a senior Professor of Psychology at Kalamazoo College, where she teaches courses in Psychology of Music and Child Development. She maintains a blog entitled What Shapes Film?

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